“Sentinel lymph node biopsy will not identify metastases in 3% of patients with node-positive disease, but has the potential to expose fewer patients to the morbidity of a complete lymphadenectomy”, write Emma Rossi, from the University of North Carolina in Chapel Hill, USA, and co-authors in The Lancet Oncology.

They add: “These results are generalisable because the study included surgeons who were novices to the technique at trial inception.”

At least one SLN was mapped successfully in 86% of patients and para-aortic SLN was detected in 23% of patients. Patients had a median of two SLNs removed and an average of 19 nodes removed in total; adequate lymphadenectomy, defined as 10 or more lymph nodes, was achieved in 84%.

In all, 41 patients had positive nodes. Of the 293 patients who had at least one SLN mapped, 36 were positive and disease was correctly identified by mapping in 35 of these patients, making SLN mapping 97.2% sensitive for nodal metastases.

Furthermore, 257 of the 258 patients with negative SLN results were confirmed as having negative non-SLNs, giving a negative predictive value of 99.6%.

And post-hoc analysis indicated that pathologically identified SLN specimens were significantly more likely to be positive for metastases than non-SLN specimens, at 5% of 1098 versus 1% of 5416, the researchers add.

They note that all patients with node-positive disease had at least one risk factor for lymph node metastases, such as lymphovascular space or myometrial invasion, or lower uterine segment involvement.

Of the patients with positive SLNs, 60% had disease only in the SLN and 40% had non-SLN metastases. SLN metastases represented the largest tumour volume in 83% of the patients, but 19 patients had low-volume SLN disease detected via ultra-staging for micrometastases or with immunohistochemistry.

The researchers observe that the SLNs were the most distal level of metastatic disease in 80% of 35 patients. “In other words, the sentinel lymph nodes did not reflect the extent of affected nodal basins in 20% of cases of stage IIIC disease”, the authors write. Three patients had para-aortic region SLNs and one an isolated para-aortic SLN.

With their findings confirming earlier results from smaller series, the team concludes: “The aggregate of evidence addressing the accuracy of the technique suggests that sentinel-lymph-node biopsy can detect metastatic disease for endometrial cancer with a sensitivity similar to that for breast cancer, melanoma, and vulvar cancers, all tumours for which sentinel-lymph-node biopsy is an accepted standard of care in staging and surgical management.”